CALBIRDS - Message Board

Birders,

I am spectacularly unqualified to comment on the Taiga vs. Tundra Bean Goose
issue, but I can provide some morphological data provided by Ruokenen et al. in
their recent (2008) paper. The complete citation is: Ruokonen, M., K. Litvin,
and T. Aarvak. 2008. Taxonomy of the bean goose - pink-footed goose. Molecular
Phylogenetics and Evolution 48:554-562.

Note that the AOU (48th supplement, 2007) basically followed Sangster and Oreel
(Dutch Birding 18:310-316, 1996) in splitting the complex as follows:
Taiga Bean-Goose, Anser fabalis
Considered monotypic, but clinal variation through formerly recognized
subspecies:
middendorffii (eastern taiga)
johanseni (central taiga)
fabalis (western taiga)
Tundra Bean-Goose, Anser serrirostris
Considered monotypic, but clinal variation through formerly recognized
subspecies:
serrirostris (eastern tundra)
rossicus (western tundra)

The more recent molecular paper by Ruokonen et al. realigns the split to include
two lineages at the species level:
Anser middendorffii (eastern taiga)
Anser fabalis (including ssp. fabalis, rossicus and serrirostris, thus
including all tundra plus western taiga)

Sangster and Oreel (at least as summarized in the Ruokonen et al. paper) seem to
suggest johanseni (central taiga) is not valid, but instead represents
intergrades between middendorffii and fabalis (and that such intergradations is
rarer than had previously been thought.

So the taxonomy still seems unsettled, though the AOU treatment above is
"official" at this point. From a California context, the important point is
that middendorffii and serrirostris, the two subspecies "most likely" to show up
here, are considered separate species in either treatment.

The main point of this message is to quote the measurement table included in
Ruokonen et al. Three bill measurements were found to be useful (I have not
heard of other characters suggested, but the recent Birding World paper which I
have not seen should be consulted; AOU 2007 implies that there are some color
and vocal differences):

middendorffii
Bill length 69.7 (SD=4.98)
Bill height 34.1 (SD=2.80)
Nail length 17.5 (SD=1.46)
Grinning patch height 8.4 (SD=1.04)

serrirostris
Bill length 62.9 (SD=3.00)
Bill height 33.8 (SD=1.52)
Nail length 18.2 (SD=1.84)
Grinning patch height 7.7 (SD=1.12)

fabalis
Bill length 61.5 (SD=4.24)
Bill height 30.5 (SD=1.89)
Nail length 15.3 (SD=1.11)
Grinning patch height 5.8 (SD=1.18)

rossicus
Bill length 57.8 (SD=2.42)
Bill height 30.7 (SD=1.52)
Nail length 16.5 (SD=0.84)
Grinning patch height 7.29 (SD=1.01)

So unless there are other (plumage) characters that are useful, you are
basically looking for roughly a 5 mm difference in bill length, with
middendorffi having a longer but relatively less deep bill. There are even
smaller differences in bill height, nail length and grinning patch height. And
note that there is a little bit of overlap between the two relevant taxa in most
or all bill structure characters.

My head is spinning....

Kimball L. Garrett
Ornithology Collections Manager
Natural History Museum of Los Angeles County
900 Exposition Blvd.
Los Angeles, CA 90007 USA
213-763-3368
kgarrett@...